This question is about atoms, molecules and nanoparticles - AQA - GCSE Chemistry - Question 3 - 2016 - Paper 2
Question 3
This question is about atoms, molecules and nanoparticles.
Different atoms have different numbers of sub-atomic particles.
(a) An oxygen atom can be represented as... show full transcript
Worked Solution & Example Answer:This question is about atoms, molecules and nanoparticles - AQA - GCSE Chemistry - Question 3 - 2016 - Paper 2
Step 1
Explain why the mass number of this atom is 16.
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Answer
The mass number of the oxygen atom is 16 because it is the total number of protons and neutrons in the nucleus. In this case, the oxygen atom has 8 protons and 8 neutrons, giving a mass number of 8 + 8 = 16.
Step 2
Explain why $^{12}_{6}C$ and $^{14}_{6}C$ are isotopes of carbon.
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Answer
The isotopes 612C and 614C are both forms of carbon that have the same number of protons, which is 6. However, they differ in the number of neutrons: 612C has 6 neutrons, while 614C has 8 neutrons. This difference leads to the variations in their mass numbers, but both isotopes maintain the same atomic number, which is characteristic of carbon.
Step 3
Complete Figure 3 to show the arrangement of the outer shell electrons of the hydrogen and oxygen atoms in a molecule of water.
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The arrangement in Figure 3 would show two hydrogen atoms and one oxygen atom. Each hydrogen atom would be depicted with one dot (•) representing its single outer shell electron. The oxygen atom would have six unpaired electrons, depicted with four dots (•) around it to signify its four unbonded electrons and bonding with the hydrogen atoms. Thus, there would be a total of two bonding pairs.
Step 4
Name the type of bonding in a molecule of water.
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The type of bonding in a molecule of water is covalent bonding.
Step 5
Why does pure water not conduct electricity?
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Answer
Pure water does not conduct electricity because it has very few free or delocalized electrons. Additionally, pure water has no overall electric charge or ions present to carry electric current.
Step 6
How does the size of a nanoparticle compare with the size of an atom?
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A nanoparticle is larger than an atom. Generally, nanoparticles range from a few nanometers to hundreds of nanometers, while atoms are at the scale of one angstrom (0.1 nanometers).
Step 7
Suggest one reason why 1 g of cobalt oxide nanoparticles is a better catalyst than 1 g of cobalt oxide powder.
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One reason is that 1 g of cobalt oxide nanoparticles has a larger surface area compared to 1 g of cobalt oxide powder. This increased surface area allows for more active sites for reactions to occur, making the nanoparticles more effective as catalysts.
